The objective of the proposed research is the validation of a comprehensive theory of drug use which has significant potential applications in the design of programs for treatment and prevention of drug problems. The theory represents an expansion of research done over the past six years on the consumption of alcohol. That work produced a theory which successfully explained individual drinking behavior--both normal use and alcoholism--in terms of 1) certain personality dimensions of the individual and 2) the failure of the individual to achieve his level of aspiration at a particular point in life. The theory of drug use also utilizes those personality dimensions and aspiration level, and adds the additional variable of the individual's alienation from society. In terms of the theory, it is proposed to explain which people are likely to use drugs, why, when, where, and to what effect--as the theory of alcohol use did for drinkers. It is also suggested that the theory can specify ways to communicate more effectively with both actual and potential drug users, and to indicate how to modify the behavior of these people. The proposal outlines the theory in detail and then presents a research design to test the validity of that theory.